The present invention relates to a rack for transporting recorded discs, and particularly to a rack for carrying the discs through washing, rinsing and drying tanks.
Recorded discs generally comprise a circular flat plate or disc of a plastic material having a center hole therethrough and recorded information provided thereon in the form of a surface relief pattern formed along a track in the major surfaces of the disc. The surface relief patterns can be formed in a spiral groove, for example, in the surfaces of the disc. Recently there has been developed a high density recorded disc, such as a video disc, in which there are a large number of grooves per inch of the diameter of the disc, e.g. 10,000 grooves per inch (4000 grooves per cm). Because of the large number of these grooves, they are very narrow and shallow, i.e. 2.7 microns in width and 4000 Angstroms in depth. Because of the fineness of these grooves, any contaminants, such as dirt, dust or other foreign particles, can severely disrupt the operation of the disc and their presence is therefore highly undesirable.
In order to remove contaminants from the surface of the discs, there has been developed a process wherein the discs are immersed in a cleaning solution, such as an aqueous solution of organic alcohol and amines of the type commercially available as 1160B from the Shipley Company, which removes the contaminants. The discs are then rinsed in water to remove the cleaning solution. To insure complete removal of the cleaning solution and contaminants, the discs are rinsed in several baths of water, for example, three baths. The first bath removes most of the cleaning solution, the second bath removes some of the remaining cleaning solution, and the final bath removes the remainder of the cleaning solution. After rinsing the discs are dried by spraying them with an organic solvent, such as 1,1,2-trichloro-2,2,1-trifluoroethane.
The discs are carried through the cleaning, rinsing and drying operations by a conveyor having racks on which a plurality of the discs are mounted. The discs are placed on the racks, which are continuously moving, just before the washing tank and are removed from the racks after they leave the drying chamber. Thus, the racks must be constructed to permit the discs to be easily and quickly mounted on and removed therefrom without damaging the discs. Since the grooves in the discs are so numerous and of very fine dimensions, even the smallest scratch can damage enough of the grooves so as to greatly disrupt the playback of the discs. Also, the racks should be of a minimum mass so that they do not retain thereon any of the liquids through which they pass. Such retained liquid could spatter back on the discs and recontaminate them.